Electronics > Beginners
Selecting MOSFET
spec:
No sweat :)
Zero999:
Another thing to consider is the switching speed. The gate of a MOSFET looks like a capacitor who's value increases when the MOSFET starts to turn on. This is due to the Miller effect. A certain charge or number of electrons is required to fully turn on a MOSFET at a given starting drain-source voltage, a parameter known as the gate charge and is measured in nano Coulombs nC. The lower the gate charge, the better, as it's less charge is required from the driver circuit. This is not much of a problem, if the MOSFET doesn't need to be switched quickly, but at high speeds it becomes signifcant.
exe:
--- Quote from: spec on January 15, 2019, 07:35:50 am ---Attached is a list of NMOSFETs that I put together for a similar application. The $ sign indicates merit.
--- End quote ---
Love to see AO fets which I have as well because of their good performance / price ratio :) (but I haven't put into application yet). Question, was Rds@2.5V actually measured or inferred from the datasheet?
spec:
--- Quote from: exe on January 15, 2019, 10:59:15 am ---
--- Quote from: spec on January 15, 2019, 07:35:50 am ---Attached is a list of NMOSFETs that I put together for a similar application. The $ sign indicates merit.
--- End quote ---
Love to see AO fets which I have as well because of their good performance / price ratio :) (but I haven't put into application yet). Question, was Rds@2.5V actually measured or inferred from the datasheet?
--- End quote ---
Alpha and Omega (AO) Yes, they make great MOSFETs. At one time they seemed to be in the lead with performance but other manufacturers have now caught up. As you say they are still a good price though.
The figures that you see in the table are all worst-case and taken from the data sheet where possible. Where the figures are not given directly on the data sheet they are extrapolated from the closest figures. To check what is what, always read the datasheet- that is the bible.
As far as RDS goes, yes they are all worst-case with a VGS of 2V5. Don't forget though that the RDS is for a junction temperature of 25 degC and RDS increases with temperature, in most cases. So, to account for possible temperature increases, I tend to double the RDS to get a working value.
permal:
--- Quote from: spec on January 15, 2019, 08:11:00 am ---Attached below is a snapshot of my directory for PMOSFETs up to 10A, which you may be interested in:
--- End quote ---
You should put them up on Github or some such, I'm sure other people like me also struggle with this.
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